LED lamps, which utilize light-emitting diodes, are used in many displaying elements of instruments such as mobile devices, PC peripheral equipments, OA equipments, various kinds of switches, light sources for backlighting, and indicating boards. The LED lamps are strongly required not only to have high efficiency, but also to be excellent in color rendition when used for general lighting or to deliver a wide color gamut when used for backlighting. For the purpose of satisfying those requirements, it is necessary to improve fluorescent substances used in light-emitting parts of LEDs. For example, in order to increase the efficiency of lamps, it is necessary to adopt highly efficient fluorescent substances in the LEDs. Further, for improving the color rendition and for broadening the color gamut of lamps, it is desired to improve chromaticity of luminescence emitted from the fluorescent substances.
On the other hand, high load LEDs generally become so hot while working that fluorescent substances used therein are heated up to a temperature of approx. 100 to 200° C. When the fluorescent substances are thus heated, their emission intensity is generally lowered. Accordingly, it is desired that the emission intensity be less lowered even if the fluorescent substances are heated. In other words, it is desired that the temperature quenching be less induced.
As fluorescent substances improved in temperature quenching, there are known red SiAlON phosphors comprising mainly silicon and aluminum (WO2007/105631). Those phosphors are, for example, represented by the formula of (Sr1-xEux)aSibAlcOdNe, and they are improved in temperature quenching as compared with conventional phosphors such as Sr2Si5N8:Eu and CaS:Eu.